As is well known, optical image-capturing apparatuses using light beam scanning can observe high-contrast/high-resolution image information based on reflected light or fluorescent light from an object to be observed. As a result, they are particularly useful in the observation of low-contrast objects. Widely used examples include scanning laser microscopes (SLM) in biological and industrial fields and medical applications such as scanning laser ophthalmoscopes (SLO) in the field of ophthalmology.
A technology related to SLM or SLO is, e.g., a scanning method using a slit beam, which reduces the burden associated with the high-speed operation of the light scanning means and which is both highly economical and practical because the object can be imaged in real time. The following is known of this technology.
Patent Document 1 discloses a configuration for an optical microscope in which a slit-shaped light beam is scanned by the first surface of a rotating mirror to illuminate an object to be observed, and reflected light from the object to be observed is scanned using the second and third surfaces of the rotating mirror and received by a predetermined detector array.
Patent Document 2 discloses a configuration for a scanning ophthalmoscope in which a light beam shaped so as to converge linearly on the focal plane is scanned one-dimensionally to illuminate the ocular fundus of an eye to be examined, and reflected light from the ocular fundus is received via scanning means by a photodetector array corresponding to the convergence line of the light beam.
Patent Document 3 discloses a configuration for a scanning laser ophthalmoscope in which a light beam in the shape of a line is scanned one-dimensionally in the direction orthogonal to the direction of the line to illuminate an eye to be examined, and reflected light from the eye to be examined is received by a one-dimensional linear CCD array detector corresponding to the line direction of the light beam.
Patent Document 4 discloses a configuration for an ophthalmoscope in which a slit-shaped light beam is scanned by the first surface of a rotating mirror to illuminate the ocular fundus of an eye to be examined, and reflected light from the ocular fundus is scanned by the second and third surfaces of the rotating mirror and received by an array-type photodetector such as a predetermined CCD or CMOS sensor.
Non-Patent Document 1 discloses a basic configuration of a scanning confocal microscope including a scanning optical system using the obverse side and reverse side of an oscillating mirror and detecting the specular reflection of a slit-shaped light beam. The ability of this configuration to observe clear corneal tissue cells in real time with high contrast has been demonstrated experimentally.
A device which combines the technology of SLMs and SLOs scanning optical systems with the technology of interference optical systems has recently garnered attention in the fields of medicine and biology. This device is an image-capturing apparatus for tomographic information (optical coherence tomography or OCT) that uses the interference phenomenon of low-interference light beams (partially coherent light). Many technologies related to OCT have been presented. The following are some examples.
Patent Document 5 discloses an OCT configuration including an interferometer using a light source having short coherence length characteristics and an optical fiber, horizontal scanning means arranged in the optical path of probe light directed towards a sample material, and the like. The basic technology for generating a tomographic image of the sample material is disclosed in this patent document.
Patent Document 6 discloses a configuration in which the light beam is split into a reference arm and a measurement arm, and a spectroscope detects the intensity of light that appears as interference between measurement light via the measurement arm and reference light via the reference arm. This patent document discloses a configuration in which an arithmetic operation such as a Fourier transform is performed on detected signals obtained via the spectroscope to thereby allow optical tomography of transparent, partially transparent, and opaque objects.
Patent Document 7 discloses a measurement device composed of an interferometer and a spectrometer wherein the light beam from a light source is condensed linearly relative to an object to be measured, and observed light from the object to be measured is detected via the spectrometer by a two-dimensional image sensor. An arithmetic operation such as a Fourier transform is performed on the detected signals from the image sensor, and tomographic information on the object to be measured is obtained at high speed in accordance with the computational speed.
Patent Document 8 proposes an OCT configuration including an interferometer, light modulating means, light scanning means, re-scanning means, and two-dimensional image-capturing means. In this configuration, it is shown that reflection intensity information from the interior of an object can be obtained at high speed by properly processing the interference information detected from the output signals of the image-capturing means.
Non-Patent Document 2 discloses a configuration for a device combining a line scanning laser ophthalmoscope (LSLO) using a one-dimensional CCD array sensor as a detector and a spectral domain OCT (SDOCT) using an optical fiber interferometer. In this configuration, it is empirically shown that two-dimensional reflection images or tomographic images in the depth direction of the ocular fundus to be observed can be selectively imaged using a single device.